I've an error te load the file in acrobat that the file can't be found

You need to change this line:

Process.Start("AcroRd32.exe", @"openFileDialog1");

What you are passing Process.Start is: openFileDialog1 not the filename. When you put the quotes around it you are making what inside the quotes a string. You want to pass the variable, not the string.

You would want to do this to call the appropriate variable, like you did in the Message Box.